Separating devices are variously employed, in particular to separate oil from a fluid flow. For example, the oil separation from the so-called blow-by gas is an ever more important part of the crankcase ventilation system in the internal combustion engine since, on the one hand, downsizing measures have an effect on the quantity and aerosol composition of the blow-by gas while, on the other hand, intensified laws on emissions accelerate the demands on oil separating systems.
During the combustion process, blow-by gas escapes through the design-related gap between piston (ring) and cylinder wall from the combustion chamber into the crankcase or along the valve stem seals into the valve space. It contains, inter alia, engine oil, fuel remnants and condensate in the form of aerosols. This gas mixture has to be discharged from the crankcase in a controlled manner and again fed to the intake tract and thus to the combustion process in a closed circuit.
In order to keep the separating performance via the volume flow of the gas-liquid mixture at a high level in as uniform a manner as possible, switchable separating systems are mostly employed. These often comprise rigid nozzle cross sections for accelerating the gas-liquid mixture against a baffle wall or a separating medium and are combined with a spring element which opens additional nozzle cross sections as a function of the volume flow. For example, spring elements in the prior art are configured as valve platelets which at the end of a tube-like geometry fixed to the housing combined with the same form a variable nozzle cross section in the form of an annular gap. In order for a flow to flow against an adequately large area of a separating element such as in particular a baffle wall, baffle surface or a separating medium, comparatively large circumferences are necessary in many cases, which disadvantageously results in a large radial installation space. An example for such an oil separating device is disclosed in DE 103 20 215 B4. EP 2 087 213 B1 also discloses such a device for separating oil particles from the crankcase ventilation gas of an internal combustion engine.
Thus a need exists for a device for separating liquid that requires as small as possible a radial installation space while, with different magnitudes of the volume flow, ensuring oil separation which is as uniform as possible over the baffle area.